Schizophrenia
In 2017, the World Health Organization reported that schizophrenia affects approximately 0.3% to 0.7% of people globally. This mental disorder manifests through distinct clusters of symptoms that clinicians categorize as positive, negative, and cognitive. Positive symptoms include hallucinations, which occur in the lifetimes of 80% of those diagnosed with schizophrenia. Most commonly these involve hearing voices, though they can sometimes engage taste, sight, smell, or touch. The frequency of hallucinations involving multiple senses is double the rate of those involving only one sense. Delusions are often bizarre or persecutory in nature. Distortions of self-experience such as feeling that others can hear one's thoughts are also common. Negative symptoms represent deficits of normal emotional responses or thought processes. Five recognized domains include blunted affect, alogia, anhedonia, asociality, and avolition. Apathy accounts for around 50% of the most often found negative symptoms and affects functional outcome and subsequent quality of life. Cognitive deficits may be of neurocognition or social cognition. An estimated 70% of those with schizophrenia have cognitive deficits, and these are most pronounced in early-onset and late-onset illness.
Genetic factors account for between 70% and 80% of individual differences in risk of schizophrenia. Having a first-degree relative with the disease increases risk to 6.5%, while more than 40% of identical twins of those with schizophrenia are also affected. Environmental triggers interact with this genetic predisposition to influence brain development. Being raised in a city has consistently been found to increase the risk of schizophrenia by a factor of two. Childhood adversity including being bullied or abused causes toxic stress and increases the risk of psychosis. Maternal infections during pregnancy alter fetal neurodevelopment through an increase of pro-inflammatory cytokines. Poor nutrition during pregnancy is another environmental factor linked to increased risk. Cannabis use during adolescence potentially doubles the rate of developing the disease in those already at risk. Living in an urban environment during childhood or as an adult continues to elevate risk even after taking into account drug use and ethnic group. A father older than 40 years or parents younger than 20 years are also associated with higher incidence rates. Oxygen deprivation and prenatal maternal stress contribute to the complex web of gene-environment interactions that lead to disorder onset.
Diagnosis relies on criteria from either the Diagnostic and Statistical Manual of Mental Disorders published by the American Psychiatric Association or the International Statistical Classification of Diseases published by the World Health Organization. The DSM-5 requires symptoms to be present for at least six months, whereas the ICD-11 allows diagnosis after one month. One symptom must be delusions, hallucinations, or disorganized speech. A second symptom could be negative symptoms or severely disorganized behavior. Functional magnetic resonance imaging has become a tool in understanding brain activity differences in individuals with schizophrenia. Researchers have observed altered connectivity patterns within several key brain networks such as the default mode network and salience network. The Positive and Negative Syndrome Scale serves as an established tool for assessing severity of positive and negative symptoms. Newer scales like the Clinical Assessment Interview for Negative Symptoms and the Brief Negative Symptom Scale offer more specific measurements. In Australia, guidelines require symptoms to last six months or more with severe impact on ordinary functioning. UK diagnosis is based on having symptoms for most of the time for one month with significant effects on ability to work or study. Agreement between these two systems remains high despite unresolved differences regarding functional outcome requirements.
Antipsychotic medication forms the mainstay of treatment for schizophrenia. A Bayesian network meta-analysis of 212 randomized controlled trials found that all 15 antipsychotic drugs reviewed were more effective than placebo. Clozapine showed the greatest efficacy among these medications. First-generation antipsychotics like haloperidol are dopamine antagonists that block D2 receptors. Second-generation antipsychotics including olanzapine and risperidone can also affect serotonin neurotransmission. About half of those with schizophrenia will respond favorably to antipsychotics and have a good return of functioning. However, positive symptoms persist in up to a third of people. Following two trials of different antipsychotics over six weeks that prove ineffective, patients receive clozapine as treatment-resistant schizophrenia care. This drug benefits around half of this group but carries potentially serious side effects like agranulocytosis in less than 4% of people. Extrapyramidal symptoms including akathisia are associated with all commercially available antipsychotics to varying degrees. Tardive dyskinesia can occur due to long-term use developing after months or years. The antipsychotic clozapine is also associated with thromboembolism and myocarditis. In September 2024, the fixed-dose combination medication xanomeline/trospium chloride received approval for medical use in the United States.
Schizophrenia decreases life expectancy by between 10 and 28 years primarily due to association with heart disease, diabetes, obesity, poor diet, sedentary lifestyle, and smoking. Almost 40% of those with schizophrenia die from complications of cardiovascular disease which is seen to be increasingly associated. There is a higher than average suicide rate estimated at 5% to 6%, most often occurring in period following onset or first hospital admission. About 85% of people with schizophrenia remain unemployed leading to social exclusion. In 2017, the Global Burden of Disease Study estimated there were 1.1 million new cases globally. In 2022 the World Health Organization reported a total of 24 million cases worldwide. Schizophrenia causes approximately one percent of worldwide disability adjusted life years and resulted in 17,000 deaths in 2015. Social problems such as long-term unemployment, poverty, homelessness, exploitation, stigmatization and victimization are common consequences. Most people with schizophrenia live independently with community support but about 75% have ongoing disability with relapses. A strong association exists between schizophrenia and tobacco smoking with estimates ranging from 80 to 90% being regular smokers compared to 20% of general population.
Accounts of a schizophrenia-like syndrome are rare in records before the 19th century with earliest case reports appearing in 1797 and 1809. German psychiatrist Heinrich Schüle used the term dementia praecox in 1886 then Arnold Pick in 1891. Emil Kraepelin made a distinction known as the Kraepelinian dichotomy between dementia praecox and manic depression in 1893. Eugen Bleuler renamed the disorder schizophrenia in 1908 when it became evident that the condition was not degenerative dementia. Kurt Schneider categorized psychotic symptoms into two groups: hallucinations and delusions in early 20th century psychiatry. In 2013 the first-rank symptoms were excluded from DSM-5 criteria though they may assist in differential diagnosis. Subtypes classified as paranoid, disorganized, catatonic, undifferentiated, and residual are no longer recognized as separate conditions by DSM-5 or ICD-11. Before the 1960s nonviolent petty criminals and women were sometimes diagnosed with schizophrenia categorizing them as ill for not performing duties as wives and mothers. From 1960s until 1989 psychiatrists in USSR and Eastern Bloc diagnosed thousands of people with sluggish schizophrenia without signs of psychosis to confine political dissidents. The annual cost of schizophrenia in United States was estimated at $62.7 billion for year 2002 including direct costs and non-healthcare costs.
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Common questions
What percentage of people globally are affected by schizophrenia according to the World Health Organization?
The World Health Organization reported in 2017 that schizophrenia affects approximately 0.3% to 0.7% of people globally.
How much does genetic factors contribute to individual differences in risk of schizophrenia?
Genetic factors account for between 70% and 80% of individual differences in risk of schizophrenia.
Which antipsychotic medication showed the greatest efficacy among all reviewed drugs in a Bayesian network meta-analysis?
Clozapine showed the greatest efficacy among all 15 antipsychotic drugs reviewed in a Bayesian network meta-analysis of 212 randomized controlled trials.
By how many years does schizophrenia decrease life expectancy primarily due to heart disease and other complications?
Schizophrenia decreases life expectancy by between 10 and 28 years primarily due to association with heart disease, diabetes, obesity, poor diet, sedentary lifestyle, and smoking.
When did Emil Kraepelin make the distinction known as the Kraepelinian dichotomy between dementia praecox and manic depression?
Emil Kraepelin made a distinction known as the Kraepelinian dichotomy between dementia praecox and manic depression in 1893.